US2398755A - Communication system - Google Patents

Description

April 16, 1946.

J. OD. SHEPHERD COMMUNICATION SYSTEM 2 Sheets-Shee t 1 Filed June 17, 1945' INVENTOR 2m&

April 16 1946. J. OD. SHEPHERD COMMUNICATION SYSTEM Filed June 1'7; 1945 2 Sheets-Sheet. 2

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' INVENTOR 8 7 SOUND RP/PODUC/NG c3 557w D/RECT Paiented Apr. 16, 1946 UNITED STATES PATENT OFFICE 2,398,755 COMMUNICATION SYSTEM Judson OD. Shepherd, Atlanta, Ga. Application June 17, 1943, Serial No. 491,087

' 24 Claims.

This invention relates tocommunication systems, particularly those in th""field of teletypewriting and the like.

Conventional teletypewriter practice usually employs a transmitting machine and one or more receiving printers. The pressure of a keyboard key sets up signal conditions in accordance with a five place code. A start signal is then transmitted which starts distributors or the equivalent.

designating signal. Depression of a key sets up a simultaneous complex code combination. The

characteristic of a conventional telegraph circuit requires this simultaneous complex code be spread out with respect to time so that it may be transmitted as simple current conditions of the marking and spacing type. At th receiving station these time-spaced impulses are accumuiated and presented to a sensing or selecting mechanism as a complex code combination. .It will be recognized that with a five place code the translation from a simultaneous to a time-spaced'and back to a simultaneous code would be unnecessary if five separate signal channels are employed. In this case the complex simultaneous code could be transmitted and received'as such.

One of the features of this invention is the transmission of character signals from the sending to the receiving station as simultaneous code combinations. This is effected by employing five (or more) frequency channels in the voice frequency range. Each character signal comprises one or more of five different frequencies with filter arrangements at the receiving station to separate the channels to eflect the printer operations. Inasmuch as the signal frequencies are in the voice frequency range, a conventional telephone circuit may be employed for transmitting telegraph messages. This circuit may be of the commercial type used for telephone service as, for example, a local connection through one or more central offices and/or private branch exchanges, a. toll connection over any suitable intertoll circuit such as a carrier channel, physical circuit or radio link, or a private line telephone circuit. Any two telephone stations in the world equipped in ac'cordance with this invention and which may be. interconnected telephonically may be employed for transmission and reception of written messages.

The transmission of the several code elements simultaneously will .enable each complete character to be sent in approximately the same length of time as required for the transmission of each elemental signal of the conventional sequential code without decreasing the length of the individualsignal elements. omitting for the moment the limitation of sending and receiving machine speeds, such a rapid rate of transmission, or the even more rapid one considered below, would enable the economical use of relatively costly telephone facilities for telegraph purposes since the holding time would be much shorter than feasible with conventional telegraph circuits.

-Where a speed of signal transmission is em ployed which is too high for production by direct operation of a. keyboard and/or for the direct operation of a teletypewriter printer, it is necessary, in order to make the most effective use of the transmission channel, to divorce the keyboard and printer with respect to time from the communication circuit. That is, the keyboard may be operated 'at one speed, transmission effected at a much higher speed and the printer actuated at a reduced speed which may be in the order of the keyboard speed. Another feature of this'invention is the method of and means for the accomplishment of this result. In the preferred embodiment of this invention, the character signals are frequency combinations which are recorded on a record medium which is driven at a certain speed. A communication channel such asa telephone circuit is established to a distant receiving station'provided with a recorder. The record at the sending station is driven at, say, five or ten times the speed of recording and the signals are reproduced therefrom. These are transmitted to the receiving station where they are recorded at preferably the same speed as they are transmitted. It will be recognized that if the reproduction at the sending station is at five times' the speed of recording, for example, the transmission time will be one-fifth as long as the recording interval and the frequencies of the signal elements will be five times as high as those recorded. The distant medium bearing the record of received signals may then be driven at substantially the recording speed at the transmission station and signals reproduced therefrom to operate a printer at substantially the speed at which the original record was made.

strument and the telegraph are well known which will permit the inductive rangements whereby a telephone connection may be established over commercial telephone facilities and the connection employed in part for a telephone conversation and in part for transmission of atelegraph message at high speed. The telephone conversation and telegraph message transmission may be either in sequence or simultaneous. In the latter case a portion of the voice frequency spectrum is employed for the telegraph channel by filter arrangements to separate it from the telephone frequency band.

Teletypewriter exchange service is now commercially furnished from special switchboards to which patrons provided with teletypewriters are connected, usually by independent cable pairs.

These switchboards are interconnected by telegraph channels which enable a nationwide switched telegraph service to be furnished. It will be recognized that this generally parallels on a smaller scale the nationwide telephone facilities. One of the principal features of this invention f is that it permits a nationwide teletypewriter service to be ofiered as an. adjunct to telephone service and without special central ofiice switchboards, inter-exchange telegraph channel and separate telegraph loops between the central offices and the patrons premises. By merely equipping commercial telephone stations with apparatus in accordance with this invention, s'witched exchange and toll telegraph service may be furnished between them without any special central oflice, trunk or intertoll facilities whatever above those normally provided for telephone service. It may further be observed that with sufilcient speed of message transmission the higher tolls for telephone in comparison with telecopy over conventionaltelephone facilities to graph channels per minute of use may be completely or more than offset. With a five to one telegraph transmission speed, a connection may be established and used for two minutes for a telephone conversation and one minute for transmission of a high speed telegraph message, in which time a message five minutcs long at normal speed may be sent. 7 I

The provision of telegraph arrangements in accordance with this invention in conjunction with commercial telephone service may'be effected, as a feature of this invention, without physical connection between the telephone inapparatus. Means coupling of the two sets. It also is apparent that they may be acoustically couple One embodiment of this invention sets out arrangements whereby high speed or direct telegraph operation may be selectively employed. The latter corresponds generally to conventional teletypewriter practice and permits two-way done with the associated recorder. The record may then be sent to separate printer arrange-,

ments such as contemplated herein for transcription.

Likewise, a comparatively inexpensive recorder-transmitter may be provided which will permit telegraph messages to be sent back to a center. Such a recorder-transmitter in portable A further modification their papers or agencies at high speed. Another example of such application is in connection with commercialtelegraph service where the customers may be provided with a recorder-transmitter sothat they can prepare messages and transmit them to the telegraph oifice over a commercial telephone circuit for retransmission over usual telegraph facilities. Arrangements are set out herein which will enable the frequency character signals to be automatically translated into conventional teletypewriter signals or punched teletypewriter tape without decoding. This will enable a frequency record to be made of a message at the telegraph office and that record; employed to actuate conventional telegraph arrangements.

A still further feature is the provision of multiplex telegraphy using a telephone circuit. This may be effected by making a plurality of message records in accordance with this invention, simultaneously translating .them at different speeds into electrical frequency signals, combining them and transmitting them simultaneously over a single communication circuit. Filter arrangements enable each band of signals to be separated and separately recorded. By reproducing each record at an appropriate speed, each may be printed. of the latter arrangement enables a single record to be made at the receiving point and effecting the printing of the separate channels by reproducing the record successively at dilferent speeds to provide'signals of appropriate frequencies for the filters associated with the printer.

'Still another feature of this invention is inclusion of arrangements for recording telephone conversations. Inasmuch as the recording arrangements provided for use in conjunction with transmission and receipt of telegraph messages are provided to record frequencies in the voice range, they may be employed to make a record of telephone conversations. I

Additional features will be understood from the drawings and specification.

Illustrative embodiments of this invention are set out schematically by two sheets of drawings including five figures as follows:

Figure 1 shows a transmitting and a receiving station for telegraphic communication,

Figure 2 indicates arrangements which may be used for translating conventional teletypewriter perforated message tape into frequencycombination signals and impressing them on a conventional telephone circuit,

Figure 3 shows a combined transmitter and receiver which may be used, together with certain special features,

Figure 4 is a list of functions of Figure 3 which are selectable, and

Figure 5 shOWS a multiplex arrangement which may be employed with this invention.

Figure 1 shows schematically a transmitting and receiving station interconnected by conventional telephone line 25. g

A keyboard machine which may be similar to the simultaneous code producing elements of a conventional teletypewriter of familiar type is provided at the transmitter. It has five keyboard contacts I to 5, inclusive,'which are actuated in accordance with a five place code, which may be the conventional teletypewriter code, in response to the depression of any character or 6 are closed upon operating any keyboard key and provide a start signal. Keyboard machines adapted to provide the above operations are blown to the art so the showing of one her is considered unnecessary for the clear understanding of this invention.

Reference below will be made to characters. It will 'be understood thatthe term characters may be generic or information units transmitted and may mean letters, numerals or machine operations generally known as stunts.

Sources of five different frequencies are indicated schematically as Fl to F5, inclusive. These eration of any key will connect one or more of the source to a frequency combining circuit. This combining circuit may consist of five transformers similar to 1 with their primaries connected individually to the keyboard contacts. The secondaries are connected in series to amplifier 8 through contacts 9, when the latter are closed, and conductors i3| and I32. Each keyboard contact is normally connected to a resistance of which I is shown so connected to contact I.- This provides an idle circuit termination for the primaries of the transformers such as I so that the impedance characteristic of the secondary circuit will be substantially constant during character transmission irrespective of the number of keyboard contacts operated. It will be understood that any suitable frequency combining circuit and means may be employed.

Means are provided to make a record of the character designating signals. This comprises a recording arrangement of any suitable type including a record medium. This medium may be a disc or cylinder record, a magnetic tape or wire, a birefringent or optically active filament such as set out by my pending application Serial Number 423,450, filed December 18, 1941, a photographic film or any other suitable type having recording and reproducing response for the frequency ranges contemplated below. It will be understood that the recording and reproducing element or elements used will be app p ate for the type of record medium employed, and that different types may be used at the transmitting and the receiving stations. It will be assumed, for the purpose of this description, that a magnetic tape or wir will be used for a record medium s nce such arrangements are so well known, although the birefringent filament arrangement mentioned may be economically and otherwise preferable. It is designated I I- and supplied from reel I2. It is driven by pulley l3 which, in turn, is driven by constant speed motor I when clutch I5 is engaged. The latter may be engaged by en- .ergizing magnet IS. The medium H bearing a signal record is accumulated in any suitable manner as, for example by a loop, coil or the like at H, or it may be wound on a takeup reel.

The output of amplifie 8 actuates the recording element l8 which is appropriate for the recording medium employed, which, in this illus-' trative case, is a magnetic tape. Consequently, as

- the tape is being driven in a manner to be de- The operation oi anykeyboard key closes contacts 6 as stated: This completes a circuit from ground, contacts 6, armature and back contact of relay is, winding of clutch magnet l8 to battery, causing. this magnet to be operated to engage clutch l5. Cam means not shown are operatively associated with pulley l3, so that as soon as the pulley starts revolving contacts 20 are closed. The upper contact of 20 is grounded to operate relay l9 over an obvious circuit including the-lower winding of that relay. This relay locks up via its front contactand upperwin'ding to ground at contacts 6. 'The lower contact of 20 provides a multiple circuit to maintain magnet 16 operated after the back contact of relay l9 has been opened and as long as contacts 20 are closed. The latter contacts are closed substantially for the period required for the tape to be driven for the recording of a single character and then opened. This arrangement is to assure that only one character will be transmitted even if a keyboard key is held down, since with contacts 6 held closed, relay l9 will remain locked up and magnet I6, and therefore the clutch, will be recontacts 20. This assures that each transmitted character signal -is of the same length and recorded with the tape moving at the same speed.

It will be understood that arrangements familiar'to the practice of the teletypewriter art may be employed to accomplish their expected desirable function. For example, known arrangements may be included to assure that a keyboard key once operatively depressed will be so maintained until after the character signal has been recorded. -Interlocking arrangements which are well known may also be provided to prevent more than one key being simultaneously operated.

After the message has been recorded on tape it and it is desired to transmit it, a communication channel is established to the distant receiving point. This is schematically indicated as the wires 25 although it is to be understood that any type channel which will transmit properly the employed'frequency band of signals'may be used.

I This may be a physical telephone circuit, as shown.

a phantom circuit, a carrier channel, a radio circuit or combinations of these, and may include an acoustical path. Circuit or other ele-- ments, including repeaters, cord circuits, switching devices or otherv elements conventional to the transmission of telephone messages and switching of such circuits may be included.

Motor 26 drives pulley 21 which in turn drives the tape at a predetermined speed. The motor is supplied from an appropriate power source at terminals 28. Closure of switch 29 will start the motor by an obvious circuit including normally closed limit switch 30 which is opened upon exhaustion of the loopof tape. The speed of record into an alternating or undulatory current corresponding to the recorded signals. This current is-extended through conventional amplifier a: and is placed on the communicationcircuit as by coupling means 33. This coupling means may be of any suitable} type as, for exampla-iafl'c'oll 75o" efl'ected. Such arrangements are familiar to the teietypewriter art.

When a received message has been recorded on medium 35, the motor 51 may be started by closure 01 switch 58 which connects it to a suitable power supply at terminals 53. This motor cir- .cuit extends through limit switch 50, which stops the transmitter of a conventional telephone" in-- strument. It maybe a direct connection between the amplifier 32 and the circuit conductors,- or

any other appropriate means for placing the character signals on the communication circuit 23.

At the receiving station a record medium 35,

' which may be similar to transmitting medium 'I I,

but not necessarily so, is supplied from reel 38.

the motor when the loop of recorded tape is exhausted. Motor 51 drives pulley 6| which in turn drives the tape. A normally disengaged clutch 62 is interposed between the motor 51 and the pulley.

This clutch arrangement may be similar to clutch Pulley 3'! drives the record medium, here again assumed to be a magnetic tape. and is in turn driven by constant speed motor 33 powered from a source connected to terminals 33. The armature of relay 40 is connected in this motor circuit so that upon operation of this relay the motor will be operatively energized. The speed at which medium 35 is driven past recorder 44 is preferably the same as that of medium ll past reproducer 3 l although it may be difierent as will .be understood.

A coupling element 4|, which may be similar to the corresponding transmitter element 33, is provided to interconnect the communication circuit with the receiving apparatus. The output of element 4| is connected to the input of amplifier 42 to bring the signals to a the recording operation.

A component of the received signals is rectified and extended by conductor 43 to relay 40. It is contemplated that astart signal will be sent from the transmitting station just prior to the message. This may, for example, be the signal corresponding to the letters stunt of the teletypewriter code.- Receipt of this, or another appropriate signal, will cause relay 40 to be operated to start the motor to drive the tape. Relay 40 is slow to release to maintain the motor circuit closed between character signals.

The signals are delivered at proper level to recorder 46, which may be similar to recorder iii, to cause the received signals to be recorded on the record medium. To assure a proper recording level of the various frequencies, amplifier d2 may be provided with conventional automatic volume control means and an equalizing network. At the end of the message the suspension of received signals will cause relay Mi to release to stop the motor.

Instead of employing a special start signal, a delay circuit may be provided ahead of recorder 45 so that at the beginning of a message the first character signal will start the motor by operating relay 40 and that signal will be delivered to the recorder after sumcient delay for the tape to be brought up to full speed.

The tape bearing the record of the received signals may be stored on a takeup reel or, as shown; as a coiled loop 45.

The printer for use with the present invention may be similar to conventional teletypewriters employing a five place code. It will be assumed, but not as a limitation, that five code magnets 5| proper level for to 55, inclusive, trip five corresponding code bars acter or stunt has been selected to cause that.

character to be printed or that stunt to be I! with magnet l8.

The signals on the record medium will be picked up by an appropriate reproducer 83 and converted into an alternating or undulating current corresponding to the record signals.

- through amplifier 64 which brings it to a proper level as alternating current. This current is supplied to five band pass filters 65, each designed to pass onei of the frequencies fl to f5, inclusive. For the purpose of the immediate description, it may be assumed that frequency fl passed by the pper filter is the. same as Fl produced by the upper source at the transmitter f2 is the same as F2 and}so on:-' This further assumes that the speed of tape at the reproducer 63 is the same as that-oi tape ll at recorder 8; and that of tape 35 at recorder 44 is the same as H at reproducer 3|.

Each filter is connected to a corresponding relay of the group designated H to 15, inclusive.

Whenever a frequency element of a reproduced signal passeaone of filters 85 it will operate its corresponding relay. Consequently, for each character signal which is made up of a combination of one or more of the appropriate frequencies there will be a corresponding relay, or relays, H to 15 operated. It will be understood that the band pass filters may be made up of any appropriate elements including crystals and may include amplifyinghind equalizing arrangements so that the proper energy level may be delivered to each of relays .'H to 15, inclusive. ments may be included in .these relay or filter circuits so that direct current type relays may be employed.

Qontacts of relays-1| to 15, inclusive, are connected respectively to windings of code magnets 5| to 55, inclusive. If relay H is energized, for example, a circuit may be traced from battery, winding of magnet 5|, contact and armature of relay 7|, winding of start relay 16 to ground, resulting in the latter relay and magnet 5i operating in series. Relay 1% may be slightly slow to operate to assure the complete operation of all magnets required for multi-element character signals. Start magnet 56 is operated over an obvious circuit in response to the operation of relay 75. A similar start operation will result from operation of any of relays H to 15. inclusive, or a combination thereof over a circuit or circuits similar to the one traced. The operation of magnet 55 will cause the printer operation corresponding to the combination of magnets 5| to 55, inclusive, which was operated.

The printer and transmitter operations are separated with respect to time so that synchronizing problem usually present with teletypewriter arrangements is not involved herein. Synchronization or coordination of the printer and the reproduced signals is provided. If the printer operates faster than the character signals are picked up by reproducer 63, each character will be printed and the printer will stop until This is passed the next signal is received. This arrangement would require pulley GI to be continuously driven. Such an arrangement would not be economical of time or recording medium, and a more appropriate one in which the printer is operated at its maximum speed and a minimum amount of medium is used per unit of message time isindicated. This is effected by having the printer control the advance of the medium past reproducer 63.

Contacts I1 are provided to be closed momentarily and then openedby the printer just before the latter completes a printing or stunt operation and indicates that it is ready for a new code signal. It completes an operating circuit for relay I8 which may be traced from battery, contacts 1'I, winding of relay 18 to contact of relay 19, causing relay 18 to operate. At its lower front contact the latter completes an obvious circuit including conductor 82 to operate clutch 62 to cause the tape to be driven. Relay I8 locks up at its upper front contact under control of relay 19 so that it will remain operated after contacts 'II are opened. A component of the signal energy picked up by 53 and amplified by 64 is extended as a current condition over conductor 80 to operate relay I9. The

operation of relay I9 releases relay 78 but simultaneously grounds conductor 82 to maintain clutch 62 operated for the duration of the character signal. As soon as the pickup of that signal is completed, relay release the clutch to stop the tape between signal positions. It will be recognized that the recordings on the tapes may be for definite intervals separated from each other by blank spaces. The tape will remain stopped betwen signal positions with respect to reproducer 63 until the above operation is started over by closure of com pletion contacts 11. This will result in the printer operating at approximately its highest feasible speed since it calls for anew character signal as soon as it completes, or is about to'cornplete, each operation.

When the printer is to be started to print a message, switch 58 is closed. to start motor 51 and it is necessary to close manually switch IT, or a switch in multiple with it, to simulate the completion of a previous operation. Other means may, of course, be provided to furnish a momentary operating circuit for relay I8 as, for example, incident to the manual closure of switch 58. The switch I! or other means for starting the tape drive may be maintained manually operated until the portion of tape 35 carrying signals reaches pickup 63 as evidenced by the printer starting operating.

It will be recognized that the contacts of relay I9 may be added to relay I5 and relay I9 dispensed with since relay I6 is operated for the duration of each signal. A separate relay I9 is shownv however, to be indicative of a high speed control element for certain embodiments of this invention, which may comprise cuit to maintain the clutch 52 energized directly by an amplified component of the signal energy.

The operations described'above in connection with Figure 1 contemplated that the record medium speed at recorder I8 and reproducer 63 would be the same and, likewise, the same medium speed is employed at reproducer 3| and recorder 44. This is not necessarily true since selection of signal frequencies for use at the transmitter keyboard contacts and choice of printer filters will enable wide choice tobe made 19 will be released toground at a back- I in the recording and reproducing speeds as may be desirable in the practicing of this invention.

It will be understood that the printer arrangements to the right of the medium loop 45 may be located at some distance from the portion of the receiver to the may be transported to the reproducing and rinting elements. This will permit a plurality of' incoming message recorders to be provided with a single reproducer and printer. Likewise, at the transmitter station, a plurality of record preparers such as indicated to the left of loop Il may be provided for each reproducer 3| and associated elements. This will be desirable in certain applications of this invention since the speed of transmitting signals over line 25 will be several times faster than a keyboard may be acter in accordance with a pattern and the circuits between contacts of relays II to I5, inclusive, and magnets 5! to 55, inclusive, may be simultaneously shifted in accordance with the same pattern. Both of these types of secrecy arrangements could, of course, be simultaneously used. They are well known to the art and the showing thereof is unnecessary for clearunderstanding of their use in connection with this an electronic cirin character or stunt invention.

This invention may be practiced using conventional perforated teletypewriter tape at the transmitter. This tape may be prepared by familiar perforating means which provide character codes consisting of combinations of holes made on a five place code basis, Such a tape is indicated in Figure 2 as "II. This tape may be driven at uniform speed by sprocket wheel I02 which, in turn, is driven by constant speed motor I03. The sprocket wheel cooperates with a row of sprocket holes I08 in the tape. Instead of a sprocket driven continuously by a constant speed motor, an appropriate intermittent or stepby-step drive may be employed to advance the tape. The code punchings in the tape are sensed by any appropriate means shown here as live contact springs. These contact springs are .connected individually to five different sources of frequency generally indicated at I05, and which may be similar to the five elements indicated as generators FI to F5, inclusive, of Figure 1.

Under the tape is a contact member I05 in opposition to the ends of springs I04. As the tape, which conventionally is made of paper, is driven, contact is made between one or more of the springs I04 and member I05 for each character by virtue of the holes in the tape to result designating signals, each consisting of one or more of five different frequencies in accordance with the code. The contact of frequency bearing springs in combinations with member I06 is merely a schematic presentation to indicate any suitable means of controlling the transmission of frequency combinations left of this loop. With such an arrangement, the medium bearing a record parison with the output circuit including memassays ber I06 so that the variation of signal levelby several in comparison with one frequencygbeing transmitted will not be great. Amplifier? M1 maybe provided to bring the signals to a proper level.

It is apparent that frequency signals may be converted into a punched tape record. For example, in Figure 1 the magnets to 55, inclusive, represent the selector magnets of a printer. In-

stead of these magnets, corresponding ones of a tape perforator may be connected to contacts of relays ii to 35, inclusive, to prepare a punched teletypewriter tape. The input to the filters need not come from a record reproducer, as shown,

but may come from any source of appropriate signals as, for example, directly from line 25. Modification of the described arrangements to efiect this are believed to he well within the sphere of the skilled. It will further be recognized that the contacts of relays it to i5 may be employed to actuate directly 2. telegraph transmitter of substantially conventional type V whereby these relays may place on the distributor segments thereof the character codes for transmission as conventional teletypewriter signals. Such an arrangement would be particularly useful in connection with receipt of frequency-code messages by a commercial telegraph company frorn'its patrons for transmission over its telegraph facilities since the frequency record of the message made in the telegraph omce need not I be decoded before transmission. it may be used in its received form as a frequency signal record to a'ctuate conventional teletypewriter circuits.

's -i Figure 2' also indicates the employment of a transmitter in conjunction ,with conventional telephone station apparatus. This station may com'p'risea handset telephone lid with asubset or bell box ii i containing the usual elements including an induction coil. Inductor i it is arranged parallel to and as close as may be to the induction coil in such manner that they'will be inductively coupled so that a transformer action will result, of which the winding of inductor H2 is the primary and the winding of the induction coil of the subsetis the secondary, so that appropriate signals reaching inductor H2 from amplifier Ill! will be repeated into the telephone circuit represented by 25 which extends to the distant receiving station via intermediate cirstrumentiio. 5 .This'may be a local established manually or by dialing, or a toll corinection' including the various elements conventionally included in such radio links.

When the distant telephone is answered, ad; vice may be given orally that a message is to be transmitted so that receiving equipment such as facilities. includihg shown at the right of Figure 1 may be opera tively connected. The transmitter may then be started and the message sent. It is apparent with this arrangement that'when the telephone connection is established it may be used partly fora telephone conversation and partly for the transmission of a telegraph message. Thislikewise is true with respect to Figure l where the coupling arrangements 85; and :5! may be provided with telephone instruments. It will be obvious that instead of inductive coupling, switches may be provided at the sending and receiving stations normally arranged to connect telephone, instruments to the communication circuit represented by wires 25, said switch being adapted to disconnect the telephone instrumerits and connect at the transmitting station the sending apparatus at the left of Figure. l and, at the receiving station, the apparatus at the right of Figure 1.

Figure 3 shows schematically an embodiment of this invention which enables a single record-i ing and reproducing arrangement to be employed at a station adaptedto send and receive tele graph messages. Other features of this invention are also set out by this figure. w 1- The arrangements of Figure 3 include a mart- 5 ually operable selector switch having nine posisitions to which the cam may be rotated. All of the cams are affixed to. but insulated from, a common shaft which may be rotated manually to any of nine positions, and appropriate indi eating means may be provided so that the operator may observe readily the position the cams occupy. The circuit convention of these camswith their brushes may be described with refer.- ence to cam D. A circuit to brush a is completed in cam positions 3, 5 and '7. Brush 0, being shown distant point. For example, a telephone receiver, or the like, may be substitutedfor inductor H2 and placed over the'transmitter of the telephone instrument.

It will also be understood that the receiving station used in conjunction with the transmitter of Figure 2 may be identical with the receiver of Figure 1 as an open face arrow,indicates that it is completed for all cam positions. Brush d completes a circuit in position 8 only. Cam C indicates an other convention. Brush 5 is completed in sitions '2 through 7, inclusive. Similar conventions are used throughout this figure to indicate the cuttings of the various cams. The descrip tion of the ileum will be separated for reference by cam positions in accordance with the operations which they control as set out by Figure 4.

Figure 3 combines certain of the elements of the two halves of Figure 1. Where a specific element of Figure 1 appears in Figure 3, it bears the connectio'ii for either transformers I through Position 1 .-OH

In this position, a circuit may be traced from telephone line 25, brushes and d of cams A and B to conventional telephone instrument I30. It is assumed that telephone circuit 25 is a conventional one terminating at a manual switchboard or dial telephone office, and may normally be used exchange or toll telephone purposes. Telephone I30 may, therefore, be dial, manual common battery or magneto type, or an extension from a private branch exchange to which circuit 25 may be connected. In position 1, as well as certain others, it may be used conventionally for telephone service.

Position 2.-Recording In position 2, a telegraphic record may be prepared. Conductors I3I and I32 are indicated by Figure 1 as being connected to the secondaries of switch 9. The preparetion of the record is similar to that of Figure l with a somewhat different circuit arrangement now to be described.

The drive motor I4 has a circuit closed for it from lower power 'terminal I33 brushes b and d of cam C, limit switch 3|), motor Id to the upper terminal of power supply I33, thereby causing the motor normally to be operated in position 2. The latter circuit may also contain another switch so that the operation selection may be effected by positioning the cams and the actual start of the motor controlled b the additional switch.

Parallel circuits may be .traced from conductors I3I and I32, brushes b and c of cams D and E to the input of amplifier 32". The output of the amplifier may be traced in parallel through brushes 0 and d of cams F and G to recorder I8. The operation of the keyboard will,as described, place frequency combinations of code signals on conductors I3I and I32 and each character to be transmitted will result in start contacts 6 being closed. A circuit may be traced from ground at momentarily closed contacts 6, brushes .1: and c of cam H, the winding of clutch magnet I6 to battery and ground. The motor I I is adapted to drive the pulley I3 at a slow or fast speed depending on which of two clutches I 6'- or I3! is engaged, said difference in speed being effected by gearing I35 and I36 interconnecting pulley I3 and motor I4 through a counter shaft in which normally disengaged clutch I6 is placed for slow speed or by direct drive through clutch I34, which is also normally disengaged, for relatively high speed for operations subsequently to be described. The operation of clutch I6 will, therefore, cause the recording medium II' to be driven intermittently at a speed corresponding to the recording speed for the keyboard as set out with respect to Figure 1. Contacts 2Il-will be closed immediately after pulle I3 starts rotating to assure the complete registration of the character and that only one code signal will be produced for each character as previously described.

These operations are repeated until the complete message is recorded. It will be noted that telephone I30 may be used while recording is taking place since it is connected to line 25 via brushescanddof camsAand B.

Position 3.-Transmitting When it is desired'to transmit the message, a connection to the distant station is established, if commercial telephone service is used, and the cams are turned to position 3. In this position. reproducer 3| is connected to the input of amplifier 32' by brushes a and c of cams D and E.-

The output of the amplifieris connected to line 25 by brushes 1) and d of cams A and B. The amplifier may have a. supervisory bridge in its output circuit to hold equipment associated with Position 4.--Rcez'ving When it is desired to receive a message at hi h speed incoming over line 25, the cams are rotated to position 4. This connects line 25 to amplifier 32 via brushes a and d of cams A and B. It will be understood that the input circuit of the amplifier may include a repeating coil, or other suitable bridge may be provided, to maintain a supervisory condition on line ziwhen the ampliflier is connected to the line. The output of the amplifier is connected to recorder I8 via brushes c and d of cams F and G. A component of the signal energy is extended from the amplifier over conductor 43-8Il, brushes a and b of cam J to operate relay Ml. This relay closes an obvious circuit. to operate clutch magnet I34 to drive medium II' at high speed. The recording operation tery, thereby indicating the completion of the message. I

Position 5.-Printing When the incoming message has been recorded and it is desired to print it. the cams maybe rotated to position 5. This will connect reproducer 3| to the input of amplifier by circuits through brushes a and c of cams D and E. The output circuit of the amplifier is connected to the filters B5 of the printer via brushes b and c of cams F and G. s

It will be recalled with reference to Figure 1 that the start of printing is effected by manual closure of contacts 11. or the equivalent, until the record is presented to the reproducer. This operation is contemplated with Figure 3, and when the signals from the record are received by amplifier 32', a component thereof is extended over conductor 43'-80', brushes a and c of cam J to operate relay 19. This relay in conjunction with completion contacts 11 and relay I8 of Figure l intermittently operate clutch magnet 62' to drive the record medium I I in a series of steps each of the apparatus of Figure 8 controlled speed substantially as previously described with respect to the printing operations of It may be noted that telephone I 30 is useable while the printing operation is taking place.

Position 6.Sund recording Inasmuch as this invention employs the recording and reproduction of frequencies within the voice range it is Well adapted to be used for recording and reproducing telephone conversations. Position 6 is provided for the purpose of sound. recording.

In this position, the line 25 is. connected through brushes c and d of cams A and B with telephone I30, and also via brushes a and d of these cams with the input of amplifier 32. The output of this amplifier is connected via brushes c and d of cams F and G with recorder It; Clutch magnet I6 is energized by a circuit traceable from battery, winding of magnet I 8', brushes c and d of cam H to ground thereby causing the medium to be driven at slow speed. This will result in a record being made of the telephone conversation.

Suitable arrangements known to the art of-recording telephone conversations may be employed, including means to record both ends of the conversation at substantially the same level.

Position 7.-S0und reproducing When it is desired to play back the recorded conversation, the cams are moved to position 7. This will result in reproducer 3i being connected with the input of amplifier 32 via brushes a and c of cams D and E, and the output of the amplifier being connected to' telephone I30 via brushes b and c of cams A and B. In position 7, clutch magnet 62' is energized by a circuit which may be traced from battery, winding ofthis magnet, brushes a and d of cam I to ground, causing the recording medium II, to be driven at the same slow speed at which the recording was made. Thi will enable the recorded conversation to be reproduced in telephone I30. It will be evident that modifications of these described arrangements will enable the recorded messa e to be reproduced through a loud speaker or over a telephone connection established over line 25.

Position 8.Send direct It may be desirable to send and receive messages at normal typing speed as with conventiona1 teletypewriter practice. This will enable questions to be sent and answers received, for example. The sending operation is effected with the cams in position 8.-

In this position the conductors I3I and I32 from the transformers I are connected to the input of amplifier 32 via brushes b and c of cams D and E. The output of the amplifier is conneoted to line 25 via brushes b and d of cams A and B.

A keyboard motor I 39 is provided to control the keyboard operations. It will be recalled that in connection with Figure 1 it was mentioned that the ope'rationof the recording medium and the keyboard may be coordinated by a. suitable mechanism driven. by motor I4. In sending direct as presently being described, driving the medium is not required, so a separat arrangement is shown for this keyboard control purpose, although the motor I I with suitable arrangements obviously maybe employed. Motor I39 is energized by a circuit which may be traced from battery, motor I39, brushes (1 and b of cam I to'ground. This motor drives two cams (land Ill which are adapted to rotate together but are frictionally mounted on shaft I42. Cam I40 has a slot and is normally held against rotation by the shaft by detent I43. This detent may be withdrawn by energization of magnet I #4, thereby permit: ting cams I40 and MI to be rotated by their shaft. A. circuit to energize this magnet may be traced from ground, keyboard contacts 6, brushes a and b of cam H, back contacts of rela I65, winding of magnet Mtto battery. Consequently, the magnet withdraws detent M3 permitting the rotation of cams I40 and MI whenever a keyboard key is operated. When detent I 63 is withdrawn, the associated'contacts complete an ob-. vious circuit to operate relay I over its upper winding. The latter opens, at the operating circuit for magnet IM. This re-' lay may be slightly slow to operate to permit cam I60 to rotate its slot from a, position opposite detent I 33, so that upon release of magnet M6 the detent will ride on the-surface of cam Idfi and thereby maintain the associated contacts closed. Cams I30 and Isl will be stopped after one revolution by detent M3 engaging the slot of cam Md. This will be irrespective of whether the keyboard key has been released or held down. If the key has been released, contacts 6 will be open so that magnet I t will continue to be deenergized upon release of relay M5 at the completion of a revolution. If contacts t are maintained closed, relay I as will be held over its lower winding upon completion of a revolution of I40, thereby preventing the reenergization after contacts II are opened and closed again.

Cam I l! closes contactsQ, which may be con-' tacts I) of Figure l, or a pair inparallel therewith, to partially complete a circuit from transformers I, to provide a code signal ofpredetermined length.

Another detent or the like I46 is also opera-*1 tively associated with detent I43 and is adapted,

-when I 53 is withdrawn incident to transmitting a character, to engage the code bars or other appropriate keyboard element to assure the trans mission of the character signals for a proper interval and to prevent the operation of another key .until transmission is completed. Detent I may, of course, be actuated by another cam-to provide a difierent locking characteristic with respect to the signal transmission.

It is contemplated that motor I38 will be driven at a regulated speed which will be somewhat slower than the normal speed of the receiving printer to obviate a synchronizing problem. The latter printer will pause briefly after each opera-- tion until the next character signal is received. In this connection, means may be provided for certain stunts such as carriage return or tabulating to maintain relay I45 operated for sufficient added time to assure that the distant printer has completed its operation before the next character is sent.

brushes b of these cains. The input of It! may its back contacts, a

of magnet its until be connected conductors I21 I and I 32, to result, a in a multiple ofthe generated frequencies being transmitted. It will be. recognizedlthat the input f multiplier I41 maybe connected to conductors I andI32 through additional cams whenthey arein positionllonlyr g a a i If the frequencies F- are supplied by rotating v generators, the speed of rotation of these may be brushes a and d of cams A and B. The output of the amplifier is connected to filters 65via brushes 1) and c of cams F and G. The operation of the printer will be substantially in accordance with the description thereof in connection with Figure 1 omitting, of course, the operations concerned with the 'recordmedium which willnot be driven in this position.

If, for reasons pointed out above, it is appropriate to use in sendingdirectly a higher frequency than is furnished by generators F- for other operations of the device, it may be necessary to employ a separate set of filters 65" tuned to these particular higher frequencies. It is obvious that additional cams may be provided connected in the filter circuits to disconnect those designated 65 and substitute a set properly designed for the frequencies employed.

With reference again to Figure 1, it will be recognized that the frequencies to which filters 65 are tuned need not be the same as provided by sources F. Let it be assumed that they are respectively tuned to frequencies which are four times that of their corresponding sources F. The speed of pulley 6| when rotating may be four times that of the recording speed at the transmitter as determinedby the. speed of pulley I3. It will be recalled that filament as at the re-, producer 63 is driven in a series .of stepsreach step being at acontrolled speed and the steps l a l l accomplish this will be, obvious to the skilled, as

well as theminor. circuit rearrangement to effect the operationof this latterclutch in position 7 of thecams It will be understood in connection with Figure. 3 that additional cams not shown may be provided to effect such circuit changes or adjustments in.

bridge on eitherthe input or output circuit when themselves controlled jointly by the signals and the printer so that the record is advanced to reproduce each signal separately and is stopped to await the completion of the printing or other operation controlled by that signal. With the record being advanced at four times the recording speed of the transmitter, it followsthat the fre quency picked upbyreproducer 63 will be four times that previously-recorded by, I8 assuming, of course. that the speed of other elements will have the relation previously contemplated. This arrangement is well adapted to direct reception with the modification of Figure 3 to include the frequency multiplier I41, inwhich scase the latter would multiply the frequency arrangement is provided @with other features set out by Figure 3,.it will be necessary to have another ,clutch arrangement in addition to B2 and 1 I31 since the slowspeed driverof pulley GI will by four. If this i be four times that of the .slow speed drive of pulley I3 as controlled by clutch I6. and the associated gearing. This thirdspeed. oipulley 61' would have tobe such as to drivehmedium, I I' atthe samespeed as used for recording with the cams in position 6 for the properlreproduction of voice recording of telephone conversations Itis believed that the addition of a third clutchand gearing to they are connected to line circuit 25.

It will be further recognized that where the type of medium and record employed will permit a combined recorder-reproducer to be used, the

- arrangementsdescribed with respect to Figure and also Figure 1, may bemodified by the skilled in accordance therewith within the spirit and scope of this invention. Likewise, a single keyboard machine similar to a conventional teletypewriter may be used both as asending machine and as a printer.

This invention is well suited to multiplex op-.

eration by several different arrangements. Figure 5 is a schematic of means to provide duplex operation. Two transmitter equipments such as shown by the left portion of Figure 1 or by Figure 2, excluding the coupling facilities, are conventionally indicated as I20 and I2I. The frequency band employed by transmitter I20 may be higher than that of I2 I so thateach of the two bands may be separated as a whole from the other by filters.

, Transmitter I20 isconnected to coupler element 33 by'high" pass filter I22 and transmitter I2I is These two bands are supplied to receivers I26 and I21, respectively.

Each of these receivers may be similar to the right hand portion of Figure 1 excluding the coupling element. It is to be understood that the speed of the recording media and the frequencies employed'by I20 and I26 must be appropriately coordinated and likewise must those of I2I and I21. It will also be understood that more than two channels may be-employed by using additional bands of signal frequencies which may beseparated by suitable filters, with a separate band assigned to each channel, as will be explained more fully below. s

The arrangementshown by Figure 5 may be employed for a simultaneoustelephone and teletypewriter connection. Conventional telephone instruments may be substituted for transmitter I2I and receiver I21. Filters I23 and I25 may be arranged to pass frequencies below 2000 cycles; for

example, which provides a generallysatisfactory J voice frequency band for telephone service. Filters I22 and I24 may pass, frequencies above 2000 cycles which are suitable for teletypewriter purposes in accordance with this invention and which may be produced by transmitter I20.

Band splitters are familiar to telephonegprac-t tioe. Theyenable asingle broad band telephone 1 channel to be employed for two narrow band independent telephone circuits. Band splitting arrangements, which are located at each terminal of a line, eliminate .all frequencies above about 1700 cycles of the two telephone circuits. It applies through a low pass filter such as I23 (Figure 5) the band from one of the circuits to the broad band telephone channel. The frequency band of It may also be assumed that the speed of receiver medium 35 at recorder 44 is eight feet per second. The speed at reproduc r 63 w ll th n be four feet per second which will supply the filters fl to )5, inclusive, with the five signal frequen:

cies to which they are tuned. This is premised,

. as stated, on the medium being 'driven in steps.

This band splitting arrangement may be 'employed to receive two separate channels which may be used for independent telephone or teletypewriter channels in accordance with this invention. Likewise, each of these channels may be used for a plurality of teletypewriter channels by proper adjustment of speeds of the transmitting and receiving record media.

There is a wide choice of frequencies which may be employed at the several stages of the transmitting and receiving arrangements. The choice of frequencies of sources Fl to F5, inclusive, may depend upon the characteristics of the medium II which may be employed in view of recorder l8 and reproducer 3|, and the speed at which the medium is driven. Another factor entering into this choice will, of course, be the'ratio of speed of the medium for message transmission to that of recording at recorder l8. Still another factor is the frequency transmission characteristics of communication circuit 25. If, for example, the upper useable frequency limit of circuit 25 is 2,800 cycles per second, and a speed, ratio of eight to one is employed, the maximum frequency of sources Fl to F5, inclusive, will be 350 cycles. 1

The speed of medium35 must be appropriate for recording the signal frequencies received over line 25. On the assumption that medium 35 will be driven intermittently with a movement for,

each signal followed by a stop While that signal is being printed, it is apparent that a wide choice .of medium speeds at this reproducing point may be employed.. The latter will depend upon the eifective band separations of filters fl to f5, inclusive, which are employec An example of frequency and media speed relations which may be employed will .be illustrative on the basis of certain assumptions taken from the wide choice available. Let it be assumed, with reference to Figure 1, that the filters ii to f5, inclusive, are tuned to 1.000, 1,100, 1,200, 1,300 and 1,400 cycles per second, and each will attenuate to ineffectiveness the other frequencies. Let it also be assumed that the effective transmission band of circuit 25 is 250 to 2800 cycles per second; also that a speed ratio of transmission is eight to one and the speed of the recording medium ll at recorder I8 is one foot per second and at reproducer 3| it will be eight feet per second to yield this ratio.

The upper frequency of sources Fl to F5, in-

clusive, will be 350 cycles so that the speed ratio will not result in the upper limit of line 25 being exceeded. For direct transmission as set out by Figure 3 without a frequency multiplier, the lower frequency will be250 cycles and the five sources may provide 250, 275, 300, 325 and 350 cycles. Consequently, the frequencies transmitted over line 25 will be 2,000, 2,200, 2,400, 2,600 and 2,800 cycles per second.

one step for each signal, at this speed.

Arrangements were described above with respect to Figure 5 whereby multiplex telegraphy may be provided with respect to this invention. While there are several methods of effecting this, an extension of the example immediately above including certain fundamental assumptions therein will be illustrative of one based upon securing filterable frequency separations of each channel by speed control of the media employed. This extension contemplates four channels which may be employed simultaneously. Let it be assumed that there are four transmitting and four corresponding receiving units for the four channels. The signals from the four reproducers 3| may be combined at coupler 32 or otherwise-simultaneously placed on line circuit 25. At the receiving station the four channels may be separated by four suitable band pass filters tuned to the four channel frequencies which may be located ahead of four amplifiersfl, whereby each recorder 40 the frequency band of its channel.

Illustrative relationships between the frequencies and media speeds of the wide choice which may be used in the practice of this invention are set out in the following table:

a. (hannel 1). Speed ratio .1 1 2 ?1 4:1 8 a. Media speed at 18 (i. p. s.') 1 1 1 l (1'. Media speed at 31 (f. p. s.) 1 2 4 8 259 (E 1000 2900 r'. Frequencies of the live signal elements over line 25 325 650 i 2G0" 350 700 1400 2800 1. Media speed at 44 (f. p. s.) l 2 4 8 ,0. Media. speed at 63 (f. s.) 4 4 4 4 Such an arrangement premised on a keyboard or recording operation of '60 words per minute will enable 900 words per minute to be transmitted over communication circuit 25, consisting of 60 for channel #1, for channel #2, 240 for channel #3 and 480 for channel #4.

It is obvious that the four channels need not be used simultaneously. They may be cut into and out of service at will. It also will be recognized that the four transmitters may be located at separate points and the signals combined at a central point where the line 25 terminates. Likewise, the four channels at the receiving station may be separated and the signals thereof supplied to four receivers and printers; It will further be understood that some channels may be transmitting in one direction while others are sending in the other.

Where the above multiplex arrangement is employed in connection with systems having more than four transmitters which are intermittently used, each transmitter may be adapted to trans mit the signal frequencies of any of the four channels so that it may be used in connection with any channel when it becomes idle. This may be accomplished by driving the medium at reproducer 3l thereof at either one, two, four or eight feet per second, depending on which channel is employed. Likewise, the channels at the receiving station may be switched to various receivers.

These receivers may be arranged, in conformity at a different speed appropriate for that aces-pa tion of relays'similar to II to l5,"inclusive, supplied through five band pass filters such as 65 designed to pass the five frequencies of that channel. The operated combination of these relays the frequencies of that channel to operate a combinachannel #3 two feet per second and for channel #4 one foot per second will be proper. This will translate the frequencie of the signals of each may indicate a desired station or effect a switching operation to test aline to it for an idle condition and to connect it to the channel if it is available. It is contemplated that when a channel becomes idle, appropriate filters and their relays may be connected to it to await a station selective signal. If the station is available, a

similar signal may'be returned to the transmitter to indicate that the station is ready to receive and the message may be started. This will enable any station out of a maximum of 31 to be selected. Making selections by operating a combination of relays and returning a start signal when a ready condition prevails is well known to the communication arts and the application thereof to the present invention is believed to come well within the sphere of the skilled in this art in view of the teachings herein.

Where there is a varying volume of originating traflic to a distant point from various transmitters, the assignment of channels may be effected whereby the station with the most trafllc or longest message may be assigned the high speed channel and those with smaller amounts of traflic may be assigned other channels in accordance with their needs.' It will also be understood that a plurality of lines to various distant points maybe terminated at a center and any transmitter or receiver may be arranged to use any channel of any line.

Where a combined transmitter-receiver such as set out by Figure 3 is employed with a selective multiplex system such as described, it may be obviously modified to provide the variou media speeds at the recorder and reproducer point required depending on the particular operation and u channel employed. These speeds may be selected lay-appropriate means and effected by suitable means which may include additional clutch and gear arrangements similar to those shown.

. As a further illustration of theflexibility of this invention to meeting various communication needs, a single recorder with one set of filters and a single printer may be used with a modification of the multiplex arrangement set out above. With this arrangement the receiving medium 35 is employed to record the frequency of the signals of all four channels. The printing of the message of each channel may then be accomplished by driving the medium 35 at the reproducer 63 at the proper speeds to provide the filter fl to 15, inclusive, with the proper frequencies to operate the printer for each message in succession. That is, the record of received signals will be reproduced four times, each time channel. Assume the use of channel frequencies set out by item 8 of the above table and the characteristics of the filters contemplated in that table, and a recording speed at 44 of two feet per second. In order to print channel #1, the reproducing speed at 63 willbe eight feet per second, for channel #2 it will be four feet per second, for

channel (except channel #3 which does not need it) to 1,000, 1,100, 1,200, 1,300 and 1,400 cycles ,for which the filters are designed. Consequently,

each channel may be separately printed depending on the speed of reproduction. With this arrangement, it is necessary that the contacts of relay 19 be added to those of 16, or similar provisions made, since the combined record of the four channels will be substantially continuous and it is necessary that the start-stop operation of the medium be controlled solely by the signal channel being printed. Relay 16 will be operated only by the signals of this channel. It may also be appropriate to disable the circuit to the filters while the medium is being brought up to speed preparatory to a printer selection operation and stopped after that selection. That is, during this acceleration and deceleration interval, the signals of the other channels may be reproduced momentarily at the frequency of one of the filters which may result in a faulty selection. This disabling may be effected by having a relay or other arrangement which will be effective momentarily each time relay 18 operates and each time relay I6 releases said arrangement being adapted to open the circuit to the filters or otherwise disable it during the brief acceleration and deceleration interval. I

Hybrid coil arrangements are familiar to the telephone art. They enable a two-wire telephone circuit used for two-way conversation to be converted into the four-wire type in which a separate circuit is employed for each direction of transmission. Such arrangements may be employed at the terminals of line 25, which may be assumed to be of the two wire type, facilities at the terminal whereby a single communication circuit 25 may be used simultaneously to transmit and receive messages in accordance with this invention. Where a multiplex arrangement such as set out above is employed for four channels, with a maximum speed ratio of eight to one, a total of 1,800 words a minute may be transmitted, 900 in each direction.

. Where this invention is used in connection with commercial telephone facilities in a large organization, a few transmitters and receivers. to ether with a printer or printers, may be located at a central point or points for use with any one of various telephones. For reception of a telegraph message incident to a telephone call incoming over a telephone line, the user may. by operating a key to pickup a ating a suitable switching mechanism or by direction to the private branch exchange operator. effect connection of the call to an idle recorder which will make a record of the message for subsequent printing. Likewise, of transmitting arrangementsmay be provided so that a message may be recorded, the record placed in a' transmitter and a connection established from any appropriate telephon in the organization to a distant telephone. The connection may, at the appropriate time, be switched to the transmitter which will then send the message at the proper speed. The transfer of telephone connections is a common practice in large and small organizations, and the known-facilities therefor may be used to transfer or extend connections to a recorder or transmitter for the purposes set out.

to provide four-wire common trunk line or by actua restricted number be employed as appropriate with another.

said signals.

An extension of this arrangement for use by the public may be efiected for incoming call by arranging to have the call transferred to a bureau equipped with recorders and printers in accordance with this invention so that telegraph messages may be recorded and printed thereat for subsequent delivery to the called party. This transference may be effected in the telephone central ofllce by appropriate known means as, for example, by the inward toll operator changing a switchboard cord connection.

The practice of this invention is not limited to using signals comprising an impulse of a combination of frequencies. Each character signal may comprise a sequence of marking and spacing impulses as with conventional teletypewriter practice. A marking impulse may, for example, be 250 cycles and BOO-cycles may be employed for spacing. A substantially conventional teletypewriter may be adapted to produce from frequency sources such signals. These may be recorded, translated at a higher speed, transmitted to a distant point, recorded thereat, again translated and separated by filters to provide conventional marking and spacing impulses to actuate a teletypewriter. Such'signals may be used with various embodiments of this invention.

- The arrangements set out are indicative of the substantial flexibility available for the practice of this invention whereby various communication needs may be met. Certain features of it described in connection with'=one embodiment may It will be understood that this invention may be practiced within the spirit and scope of the appended claims with different apparatus elements and circuit arrangements than shown.

What is claimed is:

1.The methodof communication which consists in producing information designating signals each comprising one or more predetermined frequencies in accordance with a code, recording said signals, translating said recording into signals corresponding to those recorded and preparing in response to said translated signals sensible information designations corresponding thereto.

2'. The method of communication which consists in producing character designating signals, each signal comprising one or more of a plurality of predetermined frequencies in accordance with a code, translating said signals into corresponding signals, havingirequencies different from .those produced and converting the latter said signals into recorded sensible characters corresponding to those designated by said produced signals.

ing electrical signals and, in response to latter said electrical signals, preparing a sensible mformation designating record corresponding thereto.

5. The method of communication which con- 818115 in Dm S quential character designating signals to form a message with each signal consisting of one or more predetermined frequencies in accordance with a multi-place code, translating said signals into corresponding electrical signals of higher frequencies, transmitting latter said signals to a distant point, translating, a signal at a time, the signals received at said point into other corresponding signals and printing the characters represented by last said signals whereby said message is reproduced.

6. The method of communication which consists in producing sequential character designating signals to form a message, each signal comprising a single impulse of one or more predetermined frequencies in accordance with a code, transmitting said signals over a communication channel to a distant point, recording at said point the message signals, translating the recorded signals one'at a time into corresponding electrical signals, printing in response to each of latter said signals the character corresponding thereto vtoreproduce the message and controlling the translation of each signal in response to the printing of the character corresponding to the next preceding signal.

'l. The method of communication which consists in producing information designating sig- 3, The method of communication which cona sists in producing character designating signals to form a message, each signal comprising one or more predetermined different frequencies in accordance with a code, recording said signals at a particular recording speed, translating at a different speed the recording into electrical signals and printing the message in response to latter 4. The method of communication which consists in producing information designating signals, each signal comprising an impulse of one of a plurality of predetermined frequencies or a simultaneous combination of certain of said frequencies in accordance with a code, transmitting said signals to a distant point, receiving said signals at said point, recording said received signals, translating said recording into correspondnals each comprising one or more predetermined frequencies in accordance with a code, recording said signals, translating said recorded signals into corresponding electrical signals, transmitting said electrical signals to a distant point, recording the latter signals at said distant point, translating the latter recorded signals into corresponding electrical signals and recording in response to last said'signals sensible information designations corresponding thereto.

8. The method of communication which consists in producing character designating signals each comprising an impulse of one or more predetermined frequencies in accordance with a code to form a message, recording at a certain speed the message thus produced, translating at a higher speed the signal record whereby the signal frequencies are increased above, and the message interval is decreased below, the produced message, transmitting the message signals thus translated to a distant point, recording the latter signals at said distant point, translating latter said record into corresponding signals and printing said message in response to the last said signals.

9. The method of telegraphy employing record media upon which frequency signals may be recorded which consists in producing sequential spaced character designating signals to form a message, each signal comprising one or more predetermined frequencies in accordance with a code,

driving a record medium for a predetermined interval at a particular speed for each character signal produced, recording thecorresponding sig sage being shorter than the recording time for the message, transmitting the translated signals to a, distant point, recording the signals received at said point on a record mediumdriven continuously at a certain speed, driving latter said medium intermittently at a predetermined speed a signal interval at a time, translating each latter recorded signal into a corresponding electrical signal as the latter medium is being intermittently driven, printing the character corresponding to each latter said electrical signal to reproduce the message and controlling the intermittent drive of the latter medium to effect the translation of each signal in response to the printing of the character corresponding to the next preceding signal.

10. The method of communication which consists in establishing a telephone connection between two points, employing said connection for a telephone conversation and employing it for a telegraph communication, said telegraph communication being effected by producing character designating signals each signal of which consists of one or more predetermined frequencies in the voice frequency range in accordance with a code to form a message, transmitting said signals over said telephone connection from one of said points to the other of said points, receiving said signals at latter said point, making a record of said received signals and translating said record of received signals into corresponding sensible characters.

11. The method of telegraphy which consists in transmitting simultaneously a plurality of messages over a communication channel, each message comprising sequential character designating signals'with each signal consisting of one or more predetermined frequencies in accordance with a code, said frequencies 'of the signals of a particular message lying within a frequency band individual to that message with the frequency band of each message occupying a separate portion of the frequency spectrum, recording the signals of said messages at the distant terminus of the communication channel, translating into electrical signals the record successively at particular speeds with each speed corresponding to one of said messages and adapted to cause the frequencies of the translated signals of the corresponding message to be within a predetermined frequency band and printing each message sepa-. rately in response to the signals thereof being translated in latter said frequency band.

12. A communication system including'a first station, a second station, a communication ehannel interconnecting said stations, means at the first station to produce sequential character designating signals, each signal consisting of one or more predetermined frequencies in accordance with a code, means to translate said signals into corresponding signals higher in the frequency spectrum, means for transmitting latter said signals to the second station over the communication channel and means at the latter station to print characters in accordance with the signals received thereat.

13. A communication system including a record medium, means to drive the medium at a certain speed, means to record on said medium as it is being driven information designating signals, each signal'consisting of one or more predetermined frequencies in accordance with a code, means to drive the medium at a different speed from the recording speed, means to reproduce the signals corresponding to the recorded signals while the medium is being driven at latter said speed and'means responsive to said reproduced signals to record information designations corresponding to them.

14. A communicationsystem including a first station, a second station; a communication channel between said stations, means at said first station for producing sequentially character representing signals each of which comprises one f or more predetermined frequencies in accordance with a code, a record medium, means to record said signals on said medium, means to translate said recorded signals into corresponding electrical signals, means for transmitting latter said signals to said second station over said communication channel and means at the second station responsive to latter said signals received over said communication channel for printing the characters corresponding respec-.

tively to latter said signals.

15. A communication system including a communication channel interconnecting two stations, means at one of said stations for producing sequential character designatingsignals, each signal consisting of an impulse of one or more predetermined frequencies in accordance with a code, a record medium, means to drive the medium for a predetermined interval for each character signal produced, means for recording each signal on the medium as it is being driven for that signal, means for driving the medium continuously, means for translating the record on the medium into corresponding electrical signals, means for transmitting latter said signals over the communication channel to the other said station and means at latter said station responsive to signals received over said channel for printing the characters corresponding to latter said signals.

16. A communication system including a communication channel between two points, means at one of said points for transmitting over said channel to the other of said points information designating signals, each signal consisting of one or more predetermined frequencies in accordance with a code, means at the other said point for recording the signals received over said channel and means for translating the recorded signals into corresponding sensible information designations.

17. A communication system including a communication channel between two stations. means at one of said stations for transmitting over said channel to the other station spaced information designating signals, each signal consisting of one or more predetermined frequencies in accord ance with a code, a record medium at the other said station, means to drive the medium, means to record signals incoming over said channel on said medium as it is being driven, means to drive the medium intermittently, means to translate one of said recorded signals into a corresponding electrical signal each time the record is driven and means responsive to each of said electrical signals to record an information designation corresponding thereto.

18. A communication system including a first station. a second station, a communication channel between said stations, means to produce character designating signals to form a message, each signal of which consists of one or more predetermined frequencies in accordance with a code, a record medium, means to drive the record medium at a particular speed, means to record said signals on said medium as it isbeing driven,

lated into an electrical signal.

means to drive the medium at a higher speed, means to translate said record into corresponding electrical signals as it is being driven at said higher speed, means to transmit said electrical signals over said channel to said second station and means at said second station to make a record of the signals received thereat.

19. A communication system including, a first station, a second station, a communication channel between said stations, means at the first station for producing sequential spaced character designating signals each consisting of an impulse of one or more predetermined frequencies in accordance with a code, a record medium, means to drive the record medium for a predetermined interval at a particular speed for each signal produced, means to record each signal on said medium as the medium is being driven for that signal, -means to drive the medium continuously at a speed higher than the speed at which the recording was made, means to translate said record into corresponding electrical signals over the communication channel as the record is being driven at said higher speed, a record-medium at said second station, means to drive latter said medium at a certain speed, means to record on latter said medium as itis being driven signals incoming over said communication channel, means to drive latter said medium bearing'a signal record intermittently at a predetermined speed with each driving interval corresponding to the recording of one signal, means for translating each latter recorded signal into a corresponding electrical signal as the record is driven for that signal, means responsive to each latter ascents u 22. The method of transmitting information over a communication channel which" consists in producing a plurality of separate series of information representations, each series comprising a plurality of individual information designating signals with each signal consisting of one or more predetermined frequencies in accordance with a code, said frequencies of a particular series lying within a frequency band individual to that series with the frequency band of each series occupying a separate portion of the frequency spectrum, transmitting the signals of said plurality of series concurrently over said communication channel, recording the signals at the distant terminus of' the channel, translating into electrical. signals the record successively at particular speeds with each speed corresponding to one of said series and adapted to cause the frequencies of the translated signals of the latter series to occupy a predetermined frequency band and preparing a record of information representations of each series separately in response to the signals thereof being translated in latter said frequency band.

'23. The method of communication which consists in producing a plurality of separate series of information designating code signals with each signal containing at least one predetermined frequency and with the frequency of signals of said separate series occupying separate 1 portions of the frequency spectrum, concurrently said signal for printing the character corresponding thereto, and means responsive to the printing of a character to actuate latter said driving means to cause the medium to be driven for the next succeeding recorded signal to be trans- 20. A communication system including a record medium, a telephone line, means to produce sequential character designating signals each signal consisting of one or more predetermined frequencies in accordance with a code. means to record said signalson said medium. means to translate said recorded signals on said medium into corresponding electrical signals, means to transmit latter said signals over said telephone line and means to record on said medium a telephone conversation over said telephone line.

21. The method of telegraphic communication I which consists in producing character des gnating marking and spacing signals of different frequencies in accordance with a code to forms message, transmitting said signals to a distant point, receiving said signals at said point, making a recording of the frequencies of said signals, translating said recording into corresponding electrical marking and spacing signals and, in response to said electrical signals, printing the characters corresponding thereto to form a printed message.

recording the signals of said plurality of series at a certain recording speed. successively translating said recording into electrical signals at speeds corresponding to each series which will result in latter said signalsfor each series occupying a predetermined portion of the frequency spectrum and separately preparing from latter said signals information representations of each series.

24. The method of communicationwhich consists in producing a plurality of separate series of information designating impulses, with each impulse comprising a combination of one or more frequencies in accordance with a code and with filtering each reproduced impulseinto its co ponent frequencies and preparing from latt r said frequencies information representations! Jonson o'n. SHEPHERD.

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